Peppermint, mentha piperita, is a versatile plant that has been cultivated and used for centuries in a variety of natural capacities ranging from indigestion, motion sickness, gas relief and more. Because it inhibits the growth of bacteria, mouthwash and toothpaste may be among peppermint’s best known applications. However, peppermint’s soothing and relaxing properties have placed it at the forefront of herbs found to be especially beneficial when used to support respiratory disorders such as cold, cough, throat irritation, and sinus redness.
How Peppermint Works
Peppermint leaves contain rosmarinic acid, a phenol, as well as various flavonoids. Peppermint oil contains the sought after and effective ingredients, menthol and menthone. The quality of the leaves are determined by the quantity of menthol they contain, peppermint grown in the United States is typically about 70% menthol and also contains magnesium, vitamins A and C, copper, potassium, inositol, niacin, iron, iodine, sulfur, and silicon. Within the body, peppermint exhibits action against harmful organisms, is an antioxidant, and has potential to support respiratory problems. 
Peppermint and Common Respiratory Ailments
Allergies and other respiratory problems can lead to congestion in the throat, nose, bronchi, and lungs. Peppermint has an antihistamine effect, coupled with the strong, cooling action of menthol that makes it a useful decongestant. The book, “Aromatherapy: A Complete Guide to the Healing Art,” cites peppermint oil as a ketone, meaning it is able to dissolve mucus. For these reasons, menthol is commonly found in inhalers and therapeutic balms.
Peppermint and Asthma
According to research published in the July 2010 issue of “Journal of Ethnopharmacology,” it was noted that peppermint oil was found to have anti-congestive, antispasmodic (meaning it helps relax the smooth muscles of respiratory tract), and expectorant properties. This study found that 100-300 micrograms of peppermint oil relaxed the trachea in rats. 
A condition known as, “exercise-induced asthma,” occurs when asthma symptoms are brought on by physical exercise. Dr. David Kiefer, M.D., a renowned author and advocate for alternative medicine, suggests peppermint helps reduce irritation and acts as a bronchodilator by opening the airways, decreasing shortness of breath.
Peppermint is typically thought to be safe unless specific allergies exist. Care should be exercised when using the essential oils as large amounts may cause an upset stomach. Although peppermint is typically cultivated in the United States and Europe, it should not be taken for granted that all peppermint supplements are organic. Only supplements that are supplied from natural, organic, and reputable sources should be taken.